Method for the electrical production of light.



P. G. HEWITT.

METHOD FOR THE ELECTRICAL PRODUCTION OF LIGHT.

APPLICATION FILED MAR. 27, 900.

Patented Max:124, 1914.

IN VENTOH A TTOHN S WITNESSES UNITED STATES PATENT OFFICE.

PETER COOPER HEWITT, OF NEW YORK, N. Y.. ASSIGNOR. BY MESNE ASSIGNMENTS,TO COOPER HEWITT ELECTRIC COMPANY, OF HOBOKEN. NEW JERSEY, A CORPORATION OF NEW JERSEY.

METHOD FOR THE ELECTRICAL PRODUCTION OF LIGHT.

Original application filed April 11, IQBB, Serial No. 677.199.

Specification of Letters Patent.

Serial No 10,359.

To all ulmm it may concern Be it known that 1, PETER Coon-1n HEW l'll.--a citizen of the United States. residing in the borough of Manhattan. tothe city. countv. and State of New Yfll'h'. have invented certain newand useful linrovements in Methods for the, Electr cal Production ofLight, of which the following is a full. clear, and exact description. I

This application is a division of m v tormer application, Serial Number(H1199. tiled April 11th. 1898, in which former application there isclaimed only the apparatus with 'which I practice the method hereindescribed and claimed.

The objcct'of my invention is to provide a new and useful method ofproducing l ght by electricity, whereby a light of high illuurinatingpower is produced. and the 1ntensitvand color of'the light may bevaried.

l have discoyered that certain vapors ot determinable density andphysical condi tion have the property of becoming intensely lightradiant when an electric current is passed through them. Such a vapor isthe vapor of mercury. sodium, odin and other materials, each producing alight ith colors peculiar to itself; and besides simple ele mental-yvapors. other gases have this prop erty to a certain extent. Thelight-giving quality depends chiefly on the dens1ty ot the vapor, wellas the material. ln the case of mercury, which is a fair example of ametal rolatilizing' at a practical temperature, the vapor is inclosed orformed in a tube, whose ends are adapted to hold a globule of mercury.into which are led \\'ll(. for conductingthe electrical current. which,Wiresn'iay be.submerged in the volatilizable material, or not. asdesired. In case the wire orelectrode projects through the maid rial tobe volatilized. the wire be omes heat ed on'the discharge of an electriccurrent.

Wvhich, iii turn. heats the material to he volatilize'd and 'olatiliiesit. tilting the tube Withj'apor'. if" the tube is .not alreadyof'such'ateinperature that it is sntlica-ntly tull of vapors It is wellknown that a \\'l|'c leading Into an attenuated tlllll() ,|)llt.l'(becomes heated. flltllOltfJli the same sized u'ire will conductthecurrent under ordinary run 5 ditions Without heating. In thecase herethe material tfii'be volatili'zed constitutes the t-lectrtule. thecurrent heats the electrode di rert. producing the same effect. A tubeor other uitable container may he constructed holding an exact amount oivapor (or material for producing the vapor) necessarv to produce thisintense light electricallv. iii \vluch case the exact degree of vapordenity and physical condition can be produced which is most advantageousThe electrodes must be made of suclrsize as not to be deteriorated bythe electrical discharge. the vapor forming the sole path for theelectric current between the electrodes. The light action of these tubesis intermittent and the electric current impulses or oscillations can bemade with the frequency desired, and so rapid as to require a mostdelicate instrument to detect that the light is not continuous. A tubein the form described. oneqnarter of an inch in diameter and one foot inlength. will produce a light too brilliant to look at. the light being'more than a hundred candle power. The quantity of light may be varied bythe current used, from great brilliancy to the bare luminosity ofordinary vacuum tubes. or Geissler tubes. The best practical resultsrequire the use of a current of considerable quantity. This tube ispractically indestructil'ilevhaving nothing to ruin orflestroy.operating at somewhere about the temperature of 300 C, if mercury isused. In the case Where other materials are used. the tubes operate at atemperature a little above the vaporizing point. or thereabout. of thesubstance. In practice. a very agreeable light will be pro duced by thejudicious use of two or more tubes. each containing different vapors toproduce different colors.

I will describe an apparatus \vhereby my method may he carried out. andthen point out the novel features in the appended claim.

In the drawin s: Figure l is a side elevation of mu: form of a plant forproducing: the li' ht. Fig. 2 is a side elevation of a modified 'l'ormof tube of inverted U-shape with a condensing. equalizing, and inipuritya'ctaining chamber at the bend of the.

enlarged other end of the tube; and Fig. 4 is a detail view illustratinone of the proposed modes of construction made use of at the electrodes.

Similar reference letters denote similar parts throughout the severalviews. Referring to the drawings, Fig. 1, A is an electric generator. Bis a converter, C is a condenser. and D, D wires terminating in theelectrodes E. E extending into the volatilizable substance F, containedin the bulbs G, G, of the "acuum tube G.

In carrying out my methcd T use an electric current of varying voltage,which may depend upon the lengtl" of the tube G which it is desired tooperateand the quantity of light to be produced, and also upon thematerial used. I place across the wires D, D, leading to the tube G, thecondenser C, which is of suitable capacity. This condenser C, being inresonance with the tube G and current, will adjust the voltage of thecurrent in some degree to any varying resistance that may occur in thetube. The tube G is constructed with the volatile electrodes G, G and isproportioned in size to the current to be used. The resistance of thevapor in a high degree ofattenuation is greater than it is when itbecomes a little more dense; then becoming still more dense, theelectrical resistance increases so that if the electrodes overheat, thevapor grnerated will shut off the electrical current until theyare againsufficiently cooled; but with a properly constructed tube, this onlyhappens through accident. The material condensing on the sides of thetube G or in the enlarged portions thereof, Figs. 2 and 3, may returnautomatically to the volatilizable electrode or electrodes. An electrodebeing of a volatile material will never attain a temperature higher thanits vaporiz ing temperature, and the pressure and density of the vaporin the tube are controllable by the space in the tube not carryingcurrent and forming part of the inclosurc con taincd in the tube. Thetemperature of the electrodes is thus under control and governable, thevapor, as produced, absorbing the heat.

In order to produce one of my tubes, I first exhaust it to a highvacuum, hot. then turn on the electric current, and, while the currentis on, cause the vapor to flow through the tube, or generate in the tubeand flow into the pump until it has carried away with it all theimpurities existing in the tube. These vapor impurities develop in atube apparently perfectly (!Xl'l2l.llSl(.(l. on the passage of. theelectrical current. and their absolute removal and prevention fromreappearance is most easily effe ted in this manner. The quantity oflight is approximately proportional to the vapor density; a density oflow resistance makes it possible to employ a current of low voltage inproducing the light. The quantity of light is under absolute control byvarying the quantity of the current, the density of the vapor, or thenature of the vapor. As the vapor in the tube may be very attenuated insome cases, it may become necessary in the economical use of some vaporsto use a starting device to acquire the proper vapor density onstarting. Such a starting device may consist of applied or externalheat, or in creased electrical potential for the time being. Theapparatus of Fig. 1 is an example of the latter form of starting device.A condenser in resonance ,with a transformer will raise the voltage ofthe transformer to a very much higer degree than the ratio of thewindings of the transformer would call for, and therefore will overcomethe resistance at starting.

I have shown the tubes substantially in the form of an inverted U inFigs. 1 and 2, but the tubes may be in almost any she e from spiral tostraight tubes; but in the case of a U-shaped tube used for volatilematerials, I prefer to use a tube with a partition in the bottomconsisting of the material to be volatilized, or two tubes joinedtogether. In Fig. 3, the straight tube con tains a volatilized substanceat the lower end, and a solid piece of iron, or the like, suspended inthe upper enlarged end, and electric wires leading to the substance andthe piece of iron. As above stated, the enlarged portions of the tube Gafi'ord increased surface for the condensation of vapor. These enlargedportions are seen in Fig. 2 at the bulb G and in Fig. 3 at the bulbaround the electrode in the upper end of the tube. A second function ofsuch a bulb is that of a pressure equalizer. The vapor in the bulb isnot affected by the current, nor rendered luminous, as the current doesnot pass through it, and hence the vapor contained therein can act as anequalizer to give the light a uniform brilliancy and steadiness. As thevapor rises from the volatilizable substance at the electrode anygaseous impurities existing in the tube are driven by such vapor intothese bulbs out of the path of the current. The bulbs therefore servealso the purpose of chambers for re- 'taining impurities.

In Fig. 4 I have shown the leading-in wires E and E as projecting beyondthe surface of the mercury of the electrodes. It is well understood thatsuch an arrangement lowers the resistance of either electrode whenfunctioning as a cathode and thereby serves a useful purpose.

The electrical resistance of different saturated vapors varies in a verygreat degree for the same density, mercury vapor being of comparativelylow resistance and iodin vapor of high resistance. I prefer to usevapors of low resistance as more economical and more convenient.

In producing my tube containing mercury, I have found that a very smallamount of oxygen, or oxid of mercury, in the tube increases in a markeddegree the electrical resistance and impairs the light radiant quality.I have also found that the combination of two or more tubes, each givingrays of light of different color, is advantageous.

Having thus full described my invention, I claim as new an desire tosecure by Let ters Patent In a mercury vapor apparatus, the combinationwith a translating device comprising an exhausted container and mercuryelectrodes therein separated by a Va or ath. said device having arelatively higi; ea ode starting resistance and relatively low operatingresistance and means for o ierating 20 the electrodes alternately ascatho es, of a solid conducting projection above the surface of eachelectrode whereby its cathode resistance is lowered.

In testimony whereof, I have set my hand 25

